This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 0002602-1 filed in Sweden on Jul. 10, 2000; the entire content of which is hereby incorporated by reference.
The present invention relates to a single aperture simultaneous receive/transmit antenna, and more specific an integrated aperture using narrow-band parallel side-by-side slotted ridge wave-guides for simultaneous transmission and reception.
In radio communication it has often been found that the separation between the Rx and Tx signal may be a problem i certain applications. This problem is further accentuated when the development goes towards even a more dense packing in frequency between the Rx and Tx signals. At the same time it would be desirable to avoid having two separate apertures for Rx and Tx, respectively. Examples of applications are links of different types on the ground or between ground and satellites.
In order to in a same aperture integrate receive and transmit antenna for simultaneous transmission and reception there is a problem, in particular with adjacent transmit and receive frequencies. Besides it would be desirable to include matching such that power amplifiers and low noise amplifiers may be connected to a respective port without further devices necessary. The state of the art discloses generally two kinds of solutions to the basic problem. One type of known solutions utilises a reflector antenna having a two-band feeder and diplexers. Other types instead utilise two separate apertures.
For instance, U.S. Pat. No. 4,623,894 discloses a dual band array antenna having interleaved wave-guide and dipole arrays, which each operates i a different frequency band. The solution presents a mixed design having a plurality of open-ended wave-guides operating at a first frequency of a first frequency band and a plurality of micro-strip dipoles operating at a second frequency in a second frequency band. As a result two beams of two different frequency bands are independently and simultaneously steerable in a single antenna aperture.
Another U.S. Pat. No. 5,793,330 presents an interleaved planar array antenna system providing opposite circular polarisation and comprises an array of parallel rows of parallel spaced transmit dipole radiating elements and an array of parallel rows of parallel spaced receive dipole elements. The receive dipole elements are oriented orthogonal to the transmitting dipole elements. In an illustrative embodiment the antenna system operates in two 0.5 GHz bands starting at 7.25 and 7.90 GHz, respectively, using an expected frequency separation of the order of 0.65 GHz. Still another U.S. Pat No. 5,638,079 discloses a slotted wave-guide array antenna including a plurality of wave-guide elements extending in a parallel side-by-side relation, each having a radiating side including a broad wall formed with a plurality of slots and an asymmetric ridge. The slots are slanted in relation to the longitudinal axis of the antenna in alternating directions and are spaced xcexg/2 apart such as to offset phase reversal between each pair of adjacent slots. By operating each of the groups of ridge wave-guides a selectable orthogonal linear polarisation can be obtained or by operating all the ridge wave-guides together in phase quadrature a circular polarisation is generated. However, the arrangement is intended for either transmit or receive operation, but not simultaneous transmit/receive operation.
There is for instance for link applications a demand for a compact antenna array, which utilises the same aperture for simultaneous transmitting and reception. Such an array should even be able to use the same polarisation for both transmission and reception to, for instance in a link network, not even have to keep track of what could be referred to as odd or even sites regarding transmit or receive polarisation.
An antenna device for microwave transmission and reception is disclosed which utilises an array of wave-guides arranged side-by-side. In a typical embodiment of the array the wave-guides are rectangular wave-guides having a ridge and positioned in parallel to form an array of vertical or horizontal columns. Opposite to the ridge at a second wall of the rectangular wave-guide slots are provided in the front wall, each aperture wave-guide being made narrow-band tuned for a respective transmitting or a receiving frequency in order to achieve a low coupling between transmitting and receiving to facilitate simultaneous transmission and reception. Furthermore parallel to the array of ridge wave-guides a wave-guide filter may be arranged at each side forming a respective transmitting signal filter and a receiving signal filter forming a compact single aperture transmit/receive microwave antenna unit. In a general embodiment the slots are cut in a direction parallel to the extension of the wave-guide columns and arranged in a front wall facing a second wall carrying the ridge, which may be positioned symmetrically. Every second slot further being positioned displaced to each side of an EMAX line defined in the front wall. In a further embodiment either the receive or transmit portion comprises regular rectangular wave-guides which present radiating slots in their front facing side-wall. These slots are directed at an angle across the front wall of the column to thereby obtain a different polarisation between the simultaneous transmission and reception.
An antenna device according to the present invention is set forth by the independent claims 1 and 6, and further embodiments of the invention are set forth by the dependent claims 2 to 5 and 7 to 14, respectively.